In systems for analyzing process gases and combustion flue gases, such as illustrated in U.S. Pat. No. 3,960,500, a sample probe extends into a gas duct to draw a gas sample into the analyzing system. To prevent particulate matter from being entrained by the probe and entering the analyzing system, the end of the probe is covered with a filter.
Prior art filters are generally made of a rigid material, and are thus susceptible to becoming clogged with particulate matter. While means can be provided to backflush the filter, if the particulate matter is sticky it cannot be easily dislodged by normal backflushing procedures.
Another problem associated with any form of filter which is subjected to process or combustion flue gases is that of high temperatures. Combustion gases can reach temperatures of 3000.degree. F. or greater which greatly limits the materials which can be used for such a filter.
Because of this it has become desirable to develop a filter which minimizes the entrainment of particulate matter therein, can be backflushed to dislodge any particulate matter entrained therein, and which can be subjected to extremely high temperatures without any adverse effects.